1. Field of the Invention
This invention relates to inverted telephoto type wide angle objectives of high relative aperture including those having a semi-angular field of 47.degree. with a relative aperture of F/2.0, whose bulk and size is reduced and which are well corrected for aberrations.
2. Description of the Prior Art
Recently, in the field of wide angle objectives for use in single lens reflex cameras, progress has been made in the reduction of the bulk and size of the lens system and increasing of its relative aperture. Most of these wide angle objectives employ the so-called inverted telephoto type lens configuration which offers the advantage that the back focal distance can be generally elongated. On the other hand, because the symmetry of lens configuration is broken, it becomes difficult to achieve good correction of aberrations. This difficulty tends to rapidly increase as the angular field of view and the relative aperture increase and the bulk and size of the lens system is reduced.
The use of the inverted telephoto type in the design of such lens system is disclosed in, for example, U.S. Pat. Nos. 3,748,021, 3,976,366, 3,981,563, 4,013,350, 4,061,421 and 4,188,092.